The present invention generally relates to semiconductor devices, and particularly to lead-free solder interconnect structures.
As semiconductor technology reduces in size, electromigration of metals in interconnect structures may occur. Electromigration refers to the gradual movement of metal atoms caused by momentum transferred to the atoms from electrons moving in the direction of an electric field. As electron momentum is proportional to current, increased current density increases electromigration. This movement of metal atoms may lead to early failure of the semiconductor device due to defects forming in the interconnect structure. Since decreasing the size of an interconnect structure may lead to an increase in current density, reducing the effects of electromigration in turn reduces the resulting defects in the interconnect structure in favor of increased device reliability.